After the laytime has expired and the vessel is on demurrage, no exceptions or interruptions to laytime are relevant, even during force majeure events such as strikes, etc. This is based on the principle that if the charterer had completed loading or discharging within the agreed laytime, the vessel would have left the port before the force-majeure event could intervene; hence, the thumb rule once on demurrage, always on demurrage.
The term demurrage has been incorrectly extended to use in the hire or rental of assets other than ships. Loss of use resulting in additional hire is not demurrage